Discharge lamp



May 7, 1957 F. J. HlERHoLzER, JR. ETAL 2,791,679

DISCHARGE LAMP Filed Jlily 17, 1953 United States @arent 'i DISCHARGE LAMP Frank J. Hierholzer, Jr., Bloomfield, and .lohn A. Storms,

Newark, N. J., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application July 17, 1953, Serial No. 368,794 Claims. (Cl. 240g-11.4)

This invention relates to discharge lamps and, more particularly, to the base construction for a double-wall discharge lamp.

Diiculties have been experienced with double-wall discharge lamps of the prior art due partly to mechanical and chemical considerations and partly to thermal effects. The cost factor likewise has to be taken into account, and if for no other reason, would rule out any thought of integrally formed double walls. Efforts have -been made to utilize separately formed tubular walls with spacing Washers therebetween, but this again has proved unsatisfactory due largely to differentials in expansion resulting in cracked tubes, 'and also to chemical reactions occurring between the glass of the quartz inner tube and the heat-resisting type of washer material necessarily employed.

In its general aspect, the present invention contemplates a construction overcoming the prior art difficulties.

The invention also proposes `an improved commercial lamp that will be adequately rugged to withstand `all ordinary shipping and handling usages as well as long periods of use in its intended place.

More specifically, an object of the invention is to provide -a base which will receive and support both tubes without need for or introduction of intervening washers etween the tubes.

Another o'bject of the invention is to allow for differential of expansion of the tubes and avoid application of pressure from expansion of one tube upon the other.

A further object of the invention is to provide a base and assembly with the tubes and discharge electrode conducive to retention of the heat and to improve the vaporization and ionization within the lamp.

Other objects of the invention will 'appear to persons skilled in the art to which it appertains as the description proceeds, both by direct reference thereto and by implication from the context.

Referring to the accompanying drawing in which like numerals of reference indicate similar parts throughout the several views:

Figure 1 is an elevational embodying our invention;

Figure 2 is a longitudinal sectional view of one end portion of said lamp, and

Figures 3, 4 and 5 are cross-sectional views on lines III-III, IV-IV and V-V respectively of Fig. 2.

In the specific embodiment of the invention illustrated in said drawing, the reference numeral 1d designates in general the inner tube which is sealed and constitutes the discharge envelope, and is preferably made of quartz glass or the like. As both ends are made the same, it suffices to describe the showing in Fig. 2 as illustrative of bothv ends of the lamp. It will 4be observed that the end portion of said inner tube is provided with a rounded shoulder 11 in transition from the general maximum outside size of the tube down to a terminating stern 12 of View of a discharge lamp 2,791,679 Patented May 7, 1957 2 smaller outside size'. The stem is pressed into sealing engagement with a lead-in element 13 in accordance with usual lamp practice, said element and glass press being chosen to have substantially the same coeflicients of expansion for maintaining the seal-under varying temperatiires. The inner end of the lead-in element 13 is welded or otherwise made fast to an electrode post 14 projectin'g coaxiaily into the end of the tube `and mounting an emis- Sive electrode l5 within -said tube lat about the region surrounded by said shoulder 1l. Attached to the other end of the lead-in element 13 are a pair of flexible wires 16 extending to a contact member 1'7 protruding at the far end of the body i8 of the base 19 hereinafter more fully described. Said flexible wires are soldered or otherwise `secured to said Contact member and with it and said element 13 and post 14 constitute a lead-in connection for the electrode 1S.

The 'body 18 of base 19 is preferably a hollow body lof revolution with an end wall 2) having a central pas.-

sageway for the flexible wires lo Iand for a shankv portion of contact member 17. The other end of thehollow of lsaid base provides a flaring mouth 2l of appropriate dimension to engage against rounded shoulder 11 of the glass tube 1t), thereby limiting inward position of the 4base and holding said base coaxial to the tube in assembled position. kThe said body 1S is preferably of lava or equivalent material which is non-conductive electrically and which is low in heat conductivity. The lfact that the engagement between the rounded lamp shoulder 1i Iand the fiare of mouth 2i is substantially only a line contact, and that the body is a poor heat conductor, heat from the lamp is not dissipated through the base.

The exterior of the body i8 of the base around the flared mouth 21 is in the form of a coaxial longitudinal or annular neck portion 22 'at the rear end of which is a peripheral protruding enlargement 23 the forward face of which is in 4a diametric plane thereby providing a transverse seat 24. An outer or enclosing glass tubeZS surrounds inner tube l@ and has an inner diameter enabling said outer tube to be positioned upon said neck portion 22. The end edge of the outer tube is proximate to said seat 24 and accordingly retained in longitudinal disposition thereby. The seat 24 projects radially farther than the wall thickness of said outer tube, and next thereto and around the end margin of said tube are Wrappings 26 of asbestos or other suitable heat-resistant material.

A metallic ferrule or skirt 27 is applied over said wrappings 26 and over the enlargement 23, said ferrule hav- 'ing a compressible end portion comprising a circular series of fingers 28 substantially parallel to the axis of the ferrule and directed toward the yopposite end of the lamp. A clamp ring 29 is applied over the said series of fingers and compresses the same into tight clamping engagement with the wrappings 26 which are thereby caused to grip the glass outer tube 2S very securely for holding the base in assembled engagementV with the inner tube 10. Said ferrule 27 may be slid into place from the far errd of the body land has a tapered end flange 30 for engagement against a correspondingly tapered portion of the enlargement as a limiting factor. Prearranged indentations 31 are provided in the periphery of the enlangement and the metal of the ferrule is correspondingly dented at 32 to .engage therein for keeping the ferrule from rotating on the body. A resilient snap ring 33 is provided Within the ferrule and engageable against the forward edge of seat 24 to keep the ferrule from withdrawing, the ferrule having another series of dents or inward protuberances 34 for the snap ringuto seat behind. Said ferrule 27, with its snap ring 33. and

stitute the base 19.

vespecially important to avoid cooling that region.

It is now opportune to point out that the discharge tube relies upon a gas content to be operative, and inasmuch as mercury is preferred for that purpose in conjunction with some other gas, such as argon, it is important to maintain the inner tube during operation at a constant temperature above that at which mercury vaporizes. The outer tube 25 encloses the inner tube and provides a dead air space therearound for that purpose, and since support of the inner tube is in the region of the electrode, it is The substantially line contact and the low heat conductivity characteristic of the base 19 with the inner tube 10 at its rounded shoulder 11 gains this desideratum. Furthermore, the desired result is obtained with the inner tube completely sealed without having to be sealed to the base and without having to include any packing in contact with the inner tube. This last-mentioned feature is of great importance, since it has been found that with asbestos, requiring a binder, interposed in contact With a hot quartz tube and a base, that a deleterious chemical reaction takes place which ultimately adversely aiects the quartz glass rendering it porous. The invention consequently has overcome the serious problems encountered and provides a base and lamp of improved character beneficially attaining eicient operation and long life.

We claim:

l. A lamp comprising an inner envelope of lighttransmitting material terminated by a rounded shoulder portion and a constricted stem portion, electrodes in said envelope between which a discharge occurs during operation of said lamp, an ionizable medium enclosed Within said inner envelope, means sealed through said stem portion and projecting into said inner envelope and connected to said electrodes for transmitting electrical energy thereto, an outer envelope of light-transmitting material surrounding said inner envelope in spaced relation thereto, a hollow base of electrically non-conductive and low heat conductive material enclosing and extending beyond the stem portion of said inner envelope and having a neck portion interposed between said envelopes in supporting engagement with the inner envelope at the rounded shoulder portion thereof, means encircling a portion of said base clamping the base to the outer envelop-e and holding the mouth `of said neck portion in tight engagement with the inner envelope, and means carried by the end of said base opposite said neck portion and electrically joined to said sealed means for connecting the lamp with a source of electrical energy, the mouth of said neck porti-on being flared and proportioned to accommodate the rounded shoulder portion of the inner envelope in substantially line contact when said base and envelopes are assembled in normally operative relation.

2. A lamp comprising an inner tubular envelope of light-transmitting material having an ionizable medium therein and a pair of electrodes between which a discharge occurs during operation of said lamp, means sealed through said envelope for transmitting electrical energy to said electrodes, an outer tubular envelope of lighttransmitting material surrounding the said inner envelope, each end of the said inner envelope terminating in a rounded shoulder portion and a constricted stem portion, and bases at each end of said lamp holding said inner and outer envelopes in predetermined spaced relation, each of said bases comprising a hollow body of electrically non-conductive and low heat conductive material having an annular neck portion interposed between said envelopes, the Ymouth of said neck portion-being ared and proportioned to accommodate the rounded shoulder portion of the inner envelope in substantially line Contact, a metallic skirt secured to said body and clamped to the adjacent end portion of the outer envelope holding the mouth of said neck portion in tight engagement with the rounded shoulder portion of the inner envelopes, and a contact member carried by the end of said body opposite said neck portion and electrically joined to the said sealed means in the inner envelope for connecting the lamp with a source of electrical energy.

3. A lamp comprising an inner tubular envelope of light-transmitting material having an ionizable medium therein and a pair of electrodes between which a discharge occurs during operation of said lamp, means sealed through said envelope for transmitting electrical energy to said electrodes, an outer tubular envelope of lighttransmitting `material surrounding the said inner envelope, each end of the said inner envelope terminating in a rounded shoulder portion and constricted stern portion, and bases at each end of said lamp holding said inner and outer envelopes in predetermined coaxial spaced relation, each of said bases being of circular cross-section and comprising a hollow body of electrically non-conductive and low heat conductive material enclosing and extending beyond the stem portion of said inner envelope and having a peripheral enlargement terminated on a substantially diametric plane to provide a transverse seat disposed toward said envelopes, an annular neck portion projecting from said seat toward the inner and outer envelopes and in interposed relation therewith, the mouth of said neck portion being ared and proportioned to accommodate the rounded shoulder portion of the inner envelope in substantially line contact and the end edge of the outer envelope being proximate to said seat and longitudinally retained thereby, a metallic skirt secured to said body and clamped around the adjacent end portion of the outer envelope holding the mouth of said neck portion in tight engagement with the rounded shoulder portion of the inner envelope, and a Contact member carried by the end portion of said body opposite said neck portion and electrically joined to the said sealed means in the inner envelope for connecting the lamp with a source of electrical energy.

4. A larnp comprising an inner tubular envelope of light-transmitting material having an ionizable medium therein and a pair of electrodes between which a discharge occurs during opera-tion of said lamp, means sealed through said envelope for transmitting electrical energy to said electrodes, an outer tubular envelope of light-transmitting material surrounding the said inner envelope, each end of the said inner envelope terminating in a rounded shoulder portion and a constricted stern portion, and bases at each end of said lamp holding said inner and outer envelopes in predetermined coaxial spaced relation, each of said bases being of circular cross-section and comprising a hollow body of electrically non-conductive and low heat conductive material enclosing and extending beyond the stem portion of said inner envelope Iand having a peripheral enlargement terminated on a substantially diametric plane to provide a transverse seat disposed toward said envelopes and of substantially greater depth than the wall thickness of said outer envelope, an annular neck portion projecting from said seat toward the inner and outer envelopes and in interposed relation therewith, the mouth of said neck portion being flared and proportioned to accommodate the rounded shoulder portion of the inner envelope in substantially line contact and the end edge of the outer envelope being proximate to said seat and longitudinally retained thereby, a Wrapping of heat-resistant material around the end portion of said outer envelope adjacent said seat providing a filling thereat which is substantially llush with the exposed surface of the said peripheral enlargement, a compressible metallic skirt secured to said body and encasing the adjacent end portion of the outer envelope and Wrapping thercat, means compressing said skirt into tight clamping engagement with said wrapping and outer envelope and holding the mouth of said neck portion in tight engagement with the rounded shoulder portion of the inner envelope, and a contact member carried by the end portion of said body opposite said neck portion and electrically joined to the said sealed means in the inner envelope for connecting fthe lamp to a source of electrical energy.

5. A lamp comprising an inner tubular envelope of light-transmitting material having an ionizable medium therein and a pair of electrodes between which a discharge occurs during operation of said lamp, means sealed through said envelope for transmitting electrical energy to said electrodes, an outer tubular envelope of light-transmitting material surrounding the said inner envelope, each end of the said inner envelope terminating in a rounded shoulder portion and a constricted stem portion, and bases at each end of said lamp holding said inner and outer envelopes in predetermined coaxial spaced relation, each of said bases being of circular cross-section and comprising a hollow body of electrically non-conductive and low heat conductive material enclosing and extending beyond the stem portion of said inner envelope and having a peripheral enlargement terminated on a substantially diametric plane to provide a transverse seat disposed toward said envelopes and of substantially greater depth than the wall thickness of said outer envelope, an annular neck portion projecting from said seat toward the inner and outer envelopes and in interposed relation therewith, the mouth of said neck portion being ila-red and proportioned to accommodate the rounded shoulder portion of the inner envelope in substantially line contact and the end edge of the outer envelope -being proximate to said seat and longitudinally retained thereby, a wrapping of heat-resistant material around the end portion of said outer envelope adjacent said seat providing a lling thereat which is substantially ush with the exposed surface of the said peripheral enlargement, a 4compressible metallic skirt encircling said body at said peripheral enlargement and the adjacent end portion of the outer envelope and wrapping thereat, said skirt being tapered inwardly at one end to form an end ange, a resilient snap ring provided within said skirt andpretained therein lby radially spaced prot-uberances in said skirt inward from said end flange to engage the forward edge of said transverse seat and maintain said end flange in tight engagement with the peripheral enlargement, a clamping ring encircling and compressing said skirt into tight engagement with the wrapping and the outer envelope and holding said neck portion in tight engagement with the rounded -shoulder portion of the inner envelope and in spaced apart relation with the outer envelope, and a contact member carried by the end portion of said body opposite said neck portion and electrically joined to the said sealed means in the inner envelope for connecting the lamp with a source of electrical energy, said peripheral enlargement having a series of radially spaced indentations therein and said skirt being correspondingly dented and in registry therewith to pre vent the skirt from rotating on said body.

References Cited in the tile of this patent UNITED STATES PATENTS 1,838,508 Wantz Dec. 21, 1931 2,457,353 Davis Dec. 28, 1948 2,640,145 Martt May 26, 1953 

